The release of heavy metals such as arsenic and mercury into the environment is a significant industrial problem. Natural weathering processes aided by rainfall often permit transport of the heavy metal content of wastes far beyond the original area of disposal.
It has been proposed to contain wastes by combining them with materials which increase their stability and resistance to natural degradation.
U.S. Pat. No. 3,841,102 (issued Oct. 15, 1974 to Cinner, J. R., et al.) describes the treatment of waste materials with a mixture of soluble silicates and cement to prepare a stable earth-like material with entrapped pollutants.
U.S. Pat. No. 3,947,284 (issued Mar. 30, 1976 to Kitsugi, K., et al.) describes a mixture of Portland cement and gypsum useful for admixture with sludges to provide solidified cements.
U.S. Pat. No. 3,720,609 (issued Mar. 13, 1973 to Smith, C. L., et al.) describes the treatment of waste sludges with aluminum, calcium, and sulfate ions to yield a hardened composition suitable for disposal in the environment.
A report entitled "Preliminary Report of the Development of a Method for the Solidification of Process Concentrates from the Radioactive Waste Treatment at Pelindaba" by R. A. Barbour, R. F. Henwood, and H. B. Dieperink (U.S. At. Comm. Pel-102, Dec. 1965; abstracted at Chem. Abs., 67:47016h) describes a vermiculite/cement mixture held in vacuo in a steel drum fitted with an inlet pipe. Low solids alkaline aqueous wastes containing radioactive sodium are drawn into the drum. The vermiculite acts as a filtration medium and is stated to increase the wetting properties of the cement and assist in the distribution of liquid waste in the drum.
The above-described methods do not fully answer the practical requirements of large scale industrial waste disposal of heavy metal containing waste. A practical disposal method must employ readily available materials and use inexpensive processing techniques with conventional apparatus.